An extensive body of research exists regarding the removal of substances from blood products. The bulk of this research is directed at white cell reduction. See, e.g., M. N. Boomgaard et al., Transfusion 34:311 (1994); F. Bertolini et al., Vox Sang 62:82 (1992); and A. M. Joustra-Dijkhuis et al., Vox Sang 67:22 (1994). Filtration of platelets is the most common method used in white cell reduction of platelet concentrates. See, e.g., M. Bock et al, Transfusion 31:333 (1991) (Sepacell PL-5A, Asahi, Tokyo, Japan); J. D. Sweeney et al., Transfusion 35:131 (1995) (Leukotrap PL, Miles Inc., Covina, Calif.); and M. van Marwijk et al., Transfusion 30:34 (1990) (Cellselect, NPBI, Emmer-Compascuum, The Netherlands; Immugard Ig-500, Terumo, Tokyo, Japan). These current filtration mechanisms, however are not amenable for the removal of relatively low molecular weight compounds including for example psoralens, psoralen photoproducts and other compounds commonly used in treating biological fluids.
The process of adsorption has been used to isolate selective blood components onto phospholipid polymers. For example, several copolymers with various electrical charges have been evaluated for their interactions with blood components, including platelet adhesion and protein adsorption. K. Ishihara et al., J. Biomed. Mat. Res. 28:1347 (1994). Such polymers, however, are not designed for the adsorption of low molecular weight compounds.
Various dialysis means are able to remove low molecular weight compounds from plasma and whole blood. For example, dialysis can successfully remove low molecular weight toxins and pharmaceutical compounds. Thus, dialysis might be used to remove, for example, psoralens and psoralen photoproducts from blood products. Unfortunately, current dialysis procedures involve very complicated and expensive devices. As such, the use of dialysis machines would not be practical for the decontamination of a large volume of blood products.
The use of polystyrene divinylbenzene, silica gel, and acrylester polymers for the adsorption of methylene blue has previously been described. For example, PCT Publication No. WO 91/03933 describes batch studies with free adsorbent resin (e.g., Amberlites (Rohm and Haas (Frankfurt, Germany) and Bio Beads (Bio-Rad Laboratories (Munich, Germany)). Without very careful removal of the adsorbent resins after exposure to the blood product, however, these methods create the risk of transfusion of the resin particles.
In addition, devices and processes for the removal of leukocytes and viral inactivation agents (e.g., psoralens, hypericin, and dyes such as methylene blue, toluidine blue, and crystal violet) have also been disclosed. Specifically, PCT Publication No. WO 95/18665 describes a filter comprising a laid textile web which includes a mechanically stable polymeric substrate. The web itself comprises interlocked textile fibers forming a matrix with spaces and fibrillated particles disposed within the spaces. However, this device causes a significant decrease in the Factor XI activity, which may render the treated product unsuitable for its intended use.
Simpler, safer and more economical means for reducing the concentration of low molecular weight compounds in a biological composition containing cells while substantially maintaining the biological activity of the treated biological composition containing cells are therefore needed.